Design of objective with relay lens used in military sighting telescope

To meet the small size and light weight requirement of the sighting telescope, the objective using the telephoto type structure was needed. The optical characteristics and aberration characteristics of telephoto lens with relay lens were analyzed, the configuration of telephoto lens, positive field lens, and symmetric relay lens was proposed.According to the imaging features of the system, the optical power distribution formula and dimension calculation formula were derived. The telephoto lens with relay lens was designed with optical design software Zemax, the focal length was -100 mm,the entrance pupil diameter was 25 mm, the view angle was 8, and the total length was only 99.92 mm. Designing results show that the modulation transfer function of every field is above 0.2 at 40 lp/mm, satisfing the application requirements of visual optical instrument.